2. • 8295 is a dot matix printer controller
• It provides an interface for microprocessors such as
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8085 and 8086 with dot matrix printers lr7040
• The 8295 is packaged in a 40 pin dip
• It can operate both in parallel mode and serial mode
with 8085 and 8086
• 8295 includes a 40 character buffer . when the buffer
is full or a character return is received a line is printed
automatically
• The mode selection is parallel by default
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PARALLEL INTERFACE
• Two register can be accessed by the processor in the parallel
mode
• The registers are selected as follows
4. Two types of data can be written in the input data
register by the processor :
1.The command to be executed
2.The character data to be stored in the character
buffer for printing
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5. • 8295 status is available in the output status
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register at all times.
• If IBF=1 no data should be written to 8295
• DE = 1 , it is in DMA mode
• IRQ/SER pin is used an as interrupt in parallel
mode
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• 8257 IS THE DMA CONTROLLER
• CONTROL SIGNALS BETWEEN DMA AND PROCESSOR –
HOLD ,HLDA ,RD AND WR
• CONTROL SIGNALS BETWEEN 8295 AND PROCESSOR –
CS , RD ,WR ,RESET AND IRQ/SER
• CS , RD, WR PINS ARE USED TO SELECT INPUT OR
OUTPUT REGISTER
• 8295 CONTROL SIGNALS FOR THE PRINTER INCLUDE MOT
, PFM , STB , PFEED AND HOME
•
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SERIAL MODE
• IRG/SER pin is connected to the ground pin then serial mode is
enabled
• The serial baud rate is programmed by D2 , D1 , D0 data lines
• RD must be high
• CS and WR must be low
• The processor needs USART like 8251 for serial mode
